1. Field of the Invention
This invention relates to a drilling fluid composition which is stable at temperatures of up to 350.degree. F.
2. Description of the Previously Published Art
In U.S. Pat. No. 4,349,443 to Block there is disclosed an aqueous drilling fluid comprising the combination of a hydroxy containing alumina component having the formula AlO(OH) which is a viscosifier and a reaction product of a polyvinyl alcohol (PVA) and an aldehyde containing or generating agent which is a fluid loss control agent. A further improvement in the compositional ranges of this system is described in Block U.S. Reissue Application Ser. No. 446,217 filed Dec. 2, 1982, now U.S. Pat. No. RE. 31,748. Although this drilling fluid composition has been tested at temperatures as high as 122.degree. C. (252.degree. F.) as described in the patent, there is no information on how the drilling fluid would behave at deeper well depths when the temperature approaches 350.degree. F. (177.degree. C.).
An improved method of making the AlO(OH) viscosifier component for the above-described system is described by Block in U.S. Pat. No. 4,431,550. When the AlO(OH) is being formed by reacting a base and an acid it is stabilized by having present in the reaction mixture a relatively small amount of a hydroxy acid or a salt of a hydroxy acid. The hydroxy acids described are gluconic acid, tartaric acid, gallic acid, citric acid or mixtures of these acids or their salts. These acids or salts retard the formation of tri-hydrates. The amount of the retarder used is less than 5% based on the weight of the aluminum present when expressed as AlO(OH).
3. Objects of the Invention
It is an object of this invention to formulate a drilling fluid which is stable at temperatures of about 350.degree. F. (177.degree. C.).
It is a further object of this invention to add a stabilizer to a drilling fluid containing AlO(OH) as a viscosifier and polyvinyl alcohol reaction product as a water loss controller to enable the composition to remain effective at temperatures of up to about 350.degree. F. (177.degree. C.).
It is a further object of the invention to drill a bore hole into a subterranean formation using conventional bore hole drilling equipment where the drilling fluid employed is stable up to a temperature of about 350.degree. F.
It is a further object of this invention to formulate a drilling fluid which is stable in seawater at temperatures of up to about 350.degree. F. (177.degree. C.).
These and further objects will become apparent as the description of the invention proceeds.